1. Field of the Invention
The present invention relates to a radio communication system that is used in a distribution process of merchandise, for example, for managing the merchandise.
2. Description of the Related Art
In stores such as supermarkets, commodities are arranged on display racks, and different kinds of commodities are stored in a warehouse of the store or in warehouses in the process of distribution. These commodities are not just stored but need to be supplied additionally when the current stocks are consumed. Further, the commodities need to be sent out according to orders. The radio communication system is used for managing those commodities.
The radio communication system disclosed in Japanese Unexamined Patent Publication 2004-32067 utilizes an RFID technique, which is constituted with an RFID (Radio Frequency IDentification) tag comprising an antenna coil, a memory and the like, and a reader/writer module which reads information from the RFID tag and writes information to the RFID tag. The reader/writer module is connected to a host computer that performs information management.    [Patent Literature 1] Japanese Unexamined Patent Publication 2004-32067    [Patent Literature 2] Japanese Unexamined Patent Publication 2005-109603
The RFID tags are attached to the commodities so that the tags can be placed at the same position of the commodities. Commodities are transported to clients through a distribution process, which are temporarily stored in a warehouse. Thus, in the case where the commodities are piled up for storage, it is rare that the RFID tags attached to the commodities are arranged to face the same direction. Rather, the RFID tags normally face the random directions.
Returning to the reader/writer module, a single reader/writer module is used for managing a plurality of RFID tags in actual circumstances for managing the plurality of RFID tags which are attached to the commodities and accumulated in a warehouse or the like, considering the economic phase and efficiency.
The radio communication system of this kind uses a very weak power of radio waves for eliminating disturbances to other apparatuses by the radio waves. Thus, the communicable distance is limited to be within the range of about 30 cm-several m.
The RFID may face the random directions depending on the stored state of the commodities, so that there may be the case where the radio waves irradiated from the reader/writer do not reach to the RFID tags. Therefore, it is not possible to perform highly reliable reading/writing communication.